Electromagnetic indicator unit



May 12, 1959 G. L. BUSH ELECTROMAGNETIC INDICATOR UNIT Filed March 29. 1956 I l I 1 \s' 64 I6 45 K46 INVENTOR.

G. L. BUSH ATTORN EY United States Patent ELECTROMAGNETIC INDICATOR UNIT George L. Bush, Springdale, Conn., assignor to The Teleregister Corporation, Stamford, Conn., 11 corporation of Delaware Application March 29, 1956, Serial No. 574,840

10 Claims. (Cl. 340-379) This invention relates to electromagnetic indicators for selectively displaying digits or other indicia, and more particularly to indicators in which resetting of a rotatable indicator drum or other display member to a new display position is effected by a train of incoming restoration pulses which actuate the indicator by means of pawl and ratchet structure to a home position, after which the pawl and ratchet structure is actuated by incoming actuation pulses to step the indicator drum to a new display position.

In the control of indicators of the type above referred to, it has usually been the practice to employ switching contacts controlled in accordance with the movement of the indicia display member so that when the train of restoration pulses incoming from a quotation transmitting station has energized an electromagnet to step the display member around to its home position, the restoration circuit is interrupted by the contacts to prevent further stepping of the member, which contacts then switch the electromagnet to an actuation circuit whereupon the following incoming actuation pulses from the transmitting station energize the electromagnet to step the indicator member to the new display position. The switching arrangement has customarily comprised a rotatable commutator and brush arrangement such as disclosed in Haselton Patent No. 2,049,499, issued August 4, 1936, or has comprised a rotatable cam which controls switching contacts as disclosed in Frischknecht Patent No. 2,363,056, issued November 21, 1944. Such switching arrangements, however, have the disadvantages common to movable contact elements in that the contact surfaces are subject to dirt, arcing or other corrosive effects in service, and usually require periodic inspection, cleaning and adjustment to maintain them in proper operating condition.

In accordance with the instant invention the use of such switching contacts in indicators and the maintenance problems occasioned thereby are eliminated. This is effected by employing an electromagnetic armature structure that operates to stop the indicator drum or other display member when it reaches its home position in response to a train of incoming restoration pulses and holds it in that position until the restoration pulses have ceased, whereupon it releases the drum for actuation to a new display position by the following incoming actuation pulses.

An object of the invention is to provide an electromagnetic indicator unit of the character described, in which the use of electrical contacts for stopping the indicia display member in its home position preparatory to a resetting operation is obviated.

Another object is an indicator unit of the character described, in which it is not necessary to switch from a restoration circuit to a resetting circuit at the indicator unit in order to actuate the indicator display member to a new position.

A further object is to provide means operative when an electromagnetic indicator unit has reached its home position for latching the indicator in that position until the incoming restoration pulses have ceased, and then is operative to unlatch the indicator and enable it to be actuated to a new display position by incoming actuation pulses.

Additional objects and advantages will be apparent from the following detailed description of a preferred embodiment of the invention, taken in connection with the accompanying drawings in which:

Fig. 1 is a side view in elevation of an electromagnetic indicator unit embodying the principles of the invention;

Fig. 2 is a sectional view taken along the line 2-2 of Fig. 1, showing the operative positions of latching members which prevent the indicator drum from being stepped past its home position by a train of incoming restoration pulses; and

Fig. 3 shows the relative positions of the latching members after the restoration pulses have stopped and prior to a resetting operation.

Referring now to Figs. 1 and 2, the indicator unit comprises a U-shaped metal frame 10 of magnetizable material, the top and bottom walls of which are held spaced by two front corner posts 15, 15 and a third post 15', these posts having shoulders abutting the inner faces of the top and bottom walls of the frame and being secured to the outer faces of the walls, as by spinning operations. An indicator drum 12, Fig. 1, bearing the indicia to be displayed at the front of the unit is mounted on a vertical rotatable shaft 13 journaled in bearings 16 secured to the upper and lower walls.

The type of indicator illustrated is one having eleven display positions and commonly employed in stock quotation boards for posting the prices and other data in regard to stocks or commodities. For posting the hundreds, tens, units and fractions of a price, a horizontal row of four such indicators mounted adjacent to each other are employed. The drum of the right hand indicator unit in such a row displays the fractions, usually in eighths; for example, one-eighth will be indicated by displaying a 1, two-eighths by a 2, etc. The drums for the hundreds, tens and units digits are each provided with indicia 1 to 9 and 0 appearing in that order, with a blank space between the 0 and l and representing the home position of the drum. A mask 14, which is held by its spring clip edges to the corner posts 15, has an opening or window 14' through which the proper digit is displayed to indicate the setting of the drum in any of its moved positions; in its home position a blank is displayed through the mask.

The stepping mechanism preferably comprises pawl and ratchet structure, for example, a star wheel 20, Fig. 1, is secured to the shaft 13, as by a set screw, and also is secured to the indicator drum, and the star wheel is stepped around by a double pawl or fork member 18d which is a continuation of an armature 18, one of the driving legs of the fork member being seen at 18a. This type of actuator is shown and described in the foregoing Haselton and Frischknecnt patents. The driving fork and armature structure is pivotally mounted on a shaft 22 by means of an ear 18b extending from the armature and an aperture in an extension 28 of the fork. The shaft 22 is of non-magnetic material, for example, bronze, so as not to interfere with the magnetic lines of force through the armature 18. The armature has a projecting plate portion 18c to provide a flux air gap of substantial area between this portion and the lower wall of the U-shaped frame. A second air gap is present between the portion 18d of the fork structure and the upper wall of the frame. Thin brass spaced washers 24 determine and maintain these air gaps, and there is thus a substantially continuous path for the lines of magnetic flux through the frame 10, armature 18 and the core of an electromagnet 40 which is secured by a screw 42 to the rear wall of the frame 10.

The rear extension 28 of the fork 180! is secured to one end of a retractive return spring 30, Fig. 1, the other end of the spring being secured to an adjusting arm 32 pivoted at 34. An adjnstrnent screw 36 controls the p n tension exerted; o th f rk o no ma ly ho d n one leg of the fork in engagement with the star wheel, at which time the armature portion 18 is in the position shown in Fig. 3; Figs. 1 and 2 show the armature portion attracted by the core, or main pole piece, 26 of the electromagnet 40. The construction of the parts is such that energization of the electromagnet by an incoming stepping pulse will move the fork 18d and rotate the indicator drum 12 substantially one twenty-second of a revolution, at which time the armature 18 is in the position shown in Figs. 1 and 2. At the end of each stepping pulse the electromagnet is deenergized and the retractive spring 30 returns the driving fork to its former position and this rotates the drum another twenty-second of a revolution. Each two such successive movements of the fork will rotate the drum to display the next one of the indicia. The drum is held in position after each movement by a ratchet pawl or jockey spring in any suitable manner; for example, a spring pawl 38, Fig, 1, secured to a lip portion struck in from the upper wall of the U-shaped frame, has its free end cooperating with a circular row of twenty-two small holes in the upper closed end of the drum in the manner disclosed in the aforesaid Haselton patent. The ends of the winding of the electromagnet are soldered to two prongs or slip connectors 41 mounted on, but insulated from, one of the walls of the frame, for example, the bottom wall, and passing through an aperture in the rear wall thereof. These slip connectors enable the indicator unit readily to be connected to or disconnected from any particular incoming circuit in a group represented by spring contacts fixedly mounted in an indicator board structure.

An auxiliary armature 44 is pivotally mounted, by means of cars 44c, on a shaft 48 of bronze or other nonmagnetic material, the ends of the shaft being mounted in the upper and lower walls of the frame, as seen in Fig. 1, and when the electromagnet is energized by incoming pulses the auxiliary armature has an attractive force exerted thereon by an auxiliary iron pole piece 52 that surrounds and extends laterally from the core 26 of the electromagnet. Spacers 50, of nonmagnetic material, Fig. 1, are mounted on the shaft 48 and serve to centrally position the auxiliary armature. An end portion 44b of the armature provides a low reluctance flux path to the rear of the frame. Mounted on the drum shaft 13 and rotatable with the shaft and drum 12 is a control member 46 of non-magnetic material. Preferably, although not necessarily, this control member is in the form of a disk having a slotted portion 45, Figs. 2 and 3, which is oriented relative to the drum so that when the drum reaches the first half step of its home, or blank, position in response to a train of restoration pulses received by. the electromagnet, a detent 44a on the auxiliary armature 44 will enter and remain in the slot 45, as seen in Fig. 2, since the auxiliary armature 44 is attracted by the auxiliary pole piece 52 so long as the incoming restoration pulses are received by the electromagnet. In this position a lip or extension 44d on the auxiliary armature latches over the free end of the main armature 18 and prevents the further movement of the main armature and the indicator drum until after the train of restoration pulses has ceased coming in. A copper slug or washer 54 extending around the face of the auxiliary pole piece 52, see in Fig. 1, retards the rate of flux decay at that point suificiently to prevent release of the auxiliary armature so long as the restoration pulses of a train are being received.

When the train of restoration pulses has terminated, the auxiliary armature is released and moves outwardly under the influence of a retractile coil spring 56 that has one end thereof secured to an extension 44:: of the armature, the other end of the spring being secured to an arm 58 on a pivotal bracket 59, Fig. 1. The arm and bracket are adjustable, by means of an adjusting screw 60 mounted in a right angle bracket 62, to thereby turn the bracket 59 sufiiciently to adjust the tension of the spring 56 to a desired value. A stop member 64 limits the outer movement of the armature 44. When the latch portion 44d moved away from and released the main armautre 18, the refractive spring 30 actuated the main armature away from the core 26, and this resulted in another half step of the indicator drum, so that the full blank position of the drum is displayed through the opening 14'; Fig. 3 shows the position of the disk 45 at this time. After a slight interval to insure that the auxiliary armature has released and unlatched the main armature, a train of actuation pulses is transmitted by the transmitting station and the indicator drum is stepped from its home position to a moved position corresponding to the number of actuation pulses transmitted to thereby display the desired one of the indicia. The effect of the copper slug or washer 54 is local to the auxiliary pole piece 52, and does not affect the release time of the main armature 18 during the restoration and actuation operations.

It is customary to employ a train of ten restoration pulses for actuating an indicator to its home, or starting, position since ten pulses will step an indicator from any of its ten moved positions to its home position. However, with an indicator such as disclosed in which it is not necessary to switch from a restoration circuit to an actuation circuit at the indicator, it will be noted that if a train of ten restoration pulses should inadvertently be sent to the indicator when it is in its home position, the indicator would be stepped to a position adjacent to its home position, so that the first one of the following actuation pulses would be used up in ste ping the indicator to its home position and thus the remaining actuation pulses would be lost. The drum would remain at a position half-way between 0 and blank until the last actuation pulse had been received and then step to blank. The possibility of such an occurrence, however, can be avoided by causing a train of eleven restoration pulses invariably to be transmitted before the actuation pulses are sent.

For certain purposes indicators are employed which do not post a blank, but instead show the digit 0 or other character in their home positions, in which case the arcuate position of the notched portion 45 of control member 46 relative to the indicator drum 12 is oriented accordingly.

The present invention is described with reference to a specific embodiment in order to illustrate the principles thereof, but it is understood that this is not to be. considered as limiting the.- invention as defined in the ap--. pended claims.

What is claimed is;

1. In an electromagnetic indicator unit having an indicia display member rotatable to a home position and thereafter to a selected one of a plurality of display positions, an electromagnet and actuating structure responsive to a train of incoming restoration pulses for stepping the display member from a previous display position to its home position preparatory to stepping the member to a new display position, means for producing a magnetic field in response to said restoration pulses, magnetically controlled latching means including an armature attractable by said magnetic field and operative to prevent further movement of the display member by the restoration pulses, received after the display member has reached its home position, and means for retarding the rate of flux. decay of said magnetic field sufficiently to prevent release of said armature so long as said restoration pulses are being received.

2 In an electromagnetic indicator unit having an indicia display member rotatable to a hom Position and thereafter to a selected one of a plurality of display positions, an electromagnet and actuating structure responsive to a train of incoming restoration pulses for stepping the display member from a previous display position to its home position preparatory to stepping the member to a new display position, means for producing a magnetic field in response to said restoration pulses, magnetically controlled latching means including an armature attract able by said magnetic field and operative to move into latching engagement with said actuating structure and prevent further movement of the display member by the restoration pulses received after the display member has reached its home position, and means for retarding the rate of flux decay of said magnetic field sufiiciently to prevent release of said armature so long as said restoration pulses are being received.

3. In an indicator unit having an indicia display member rotatable to a home position and thereafter to a selected one of a plurality of display positions, an electromagnet and actuating structure responsive to a train of incoming restoration pulses for stepping the display memher from a previous display position to its home position preparatory to stepping the member to a new display position, magnetically controlled latching means for preventing the display member from being stepped past its home position by said restoration pulses, comprising an armature having a latching position and a releasing position and urged towards its latching position by the magnetic field of said electromagnet, a control member rotatable with said display member for timing the application of said latching means, a latch member controlled jointly by said armature and control member and movable into latching engagement with said actuating structure when the display member enters its home position to prevent further movement of the display member by the incoming restoration pulses, and means for retarding the rate of flux decay of said magnetic field sufiiciently to prevent release of said armature so long as said restoration pulses are being received.

4. An indicator unit according to claim 3, in which said control member has a configuration that normally prevents the armature and latch member from moving to latching position, but which permits them to move to latching position when the display member enters its home position.

5. In an indicator unit having an indicia display member rotatable to a home position and thereafter to a selected one of a plurality of display positions, an electromagnet having a main magnetic pole, a main armature and actuating structure and responsive to a train of incoming restoration pulses for stepping the display member from a previous display position to its home position preparatory to stepping the member to a new display position, magnetically controlled latching means for preventing the display member from being stepped past its home position by said restoration pulses, said latching means comprising an auxiliary magnetic pole for said electromagnet and an auxiliary armature attractable thereby towards a latching position by the auxiliary pole of said electromagnet, a control member rotatable with said display member for timing the application of said latching means, a latch element controlled jointly by asoe said auxiliary armature and control member and movable into latching engagement with said main armature when the display member enters its home position to prevent further stepping of the display member by the incoming restoration pulses, and means for retarding the rate of flux decay of said magnetic field sufiiciently to prevent release of said auxiliary armature so long as said restoration pulses are being received.

6. An indicator unit according to claim 5, in which said auxiliary pole extends laterally from said main pole, and the auxiliary armature extends in a direction transverse to the plane of the main armature.

7. An indicator unit according to claim 5, in which said auxiliary pole has means thereon operative to retard collapse of a flux field and maintain an attractive force on the auxiliary armature during intervals between successive restoration pulses.

8. In an indicator unit having an indicia display member rotatable to a home position and thereafter to a selected one of a plurality of display positions, an electromagnet and actuating structure including a main armature responsive to a train of incoming restoration pulses for stepping the display member from a previous display position to its home position preparatory to stepping the member to a new display position, magnetically controlled latching means for preventing the display member from being stepped past its home position by said restoration pulses, comprising an auxiliary armature urged towards a latching position by the magnetic field of said electromagnet, a control member having a track portion and rotatable with said display member, a latch member extending from said auxiliary armature and having a follower portion coacting with said track to normally hold said latch member out of latching position, said track having a configuration at one point thereof which enables the latch member to move into latching engagement with said main armature when the display member enters its home position to prevent further movement thereof by the incoming restoration pulses, and means for retarding the rate of flux decay of said magnetic field sufiiciently to prevent release of said auxiliary armature so long as said restoration pulses are being received.

9. An indicator unit according to claim 8, in which said control member has a circular configuration and said follower portion of the latch member coacts with the periphery of the control member to normally hold the latch member out of latching position, said periphery having a recess into which said follower portion enters to effect said latching engagement with the main armature.

10. An indicator unit according to claim 9, in which said control member comprises a circular disk and said follower portion coacts with the edge of the disk, said edge having a gap into which the follower portion enters to effect said latching engagement with the main armature.

References Cited in the file of this patent UNITED STATES PATENTS 2,049,499 Haselton Aug. 4, 1936 2,121,061 Townsend June 21, 1938 2,189,581 Hicks Feb. 6, 1940 2,363,056 Frischknecht Nov. 21, 1944 

